Method and apparatus for spinning artificial filaments



Patented Dec. 27, 1949 uNr-rso STATES PATENT 2,492,452 OFFICE METHOD AND APPARATUS FOR SPINNING ARTIFICIAL FILAMENTS ware No Drawing. Application January 3, 1945, Serial No. 571,195

This invention relates to improvements in the manufacture of artificial fibers from viscose.

Artificial fibers comprising regenerated cellulose from viscose are obtained by the wet spinning method, that is the viscose is spun through a spinneret into an acid spinning bath in which individual streams of viscose emerging from the spinneret are coagulated and regenerated. Under such conditions, the acid bath contains a large amount of suspended gas bubbles. Ordinarily the spinneret has a comparatively low orifice area density and the gas bubbles do not interfere with the orderly and continuous progress of the individual streams of viscose away from the face of the spinneret and the streams are separately acted upon by the bath and coagulated. However, in the manufacture of filaments which are destined for cutting into staple fibers, it is desirable to spin a'great many filaments from a singlespinneret and collect the bundle of filaments in the form of a long tow which is then fed to a staple fiber cutting mechanism. The spinnerets are made from precious metals such as platinums or the like, and for obvious rea sons of economy, must be kept as small as possible which, in the case of spinning a very large number of filaments from a single spinneret, requires a high orifice area density. When viscose is spun through such spinnerets having an orifice area density so high that the orifice area density factor K is greater than 800 when determined in accordance with the following formula D=- or its equivalent, K

Where D=orifice density, orifices/sq. in. S=periphery of the face of the jet in inches A=and area of the face of the jet in sq. inches it is a common observation that the gas bubbles which permeate the bath are attracted to and tend to adhere to or cling to the face. Under those conditions, the progress of the acid to the individual streams of viscose issuing from the spinneret away from the face into the bath is seriously hampered. The bubbles clinging to the exceedingly small unperforated portions of the face which exist between the densely packed orifices interfere with acid distribution and permit a multiplicity of the streams of raw viscose to come together without having been coagulated. As they are drawn through the spinning bath by re action of the godet wheel, the merged streams are coagulated and cemented together to form excessively large filaments or splinters which occur haphazardly throughout the final bundle. The phenomenon of gas bubble adherence to the face of the spinneret is extremely troublesome, necessitating frequent discontinuance of the spin- 10 Claims. (01. 18 8) ning operation and manual dislodgement of the gas bubbles, and requiring the spinning of a large number of ends in order to obtain a tow having sufiicient average total denier over a long period of time. The problem is encountered only in those instances when the spinneret employed has a face of small diameter and an orifice area density such that, according to the foregoing formula, the value of K is greater than 800. No satisfactory solution of theproblem has been pro pounded heretofore.

This invention has as an object improvements in the spinning of artificial fibers through spinnerets having high orifice area density. A-further object is to alter the inter-facial tensions existing at the face of such spinnerets in acid spinning baths to prevent the adherence of gas bubbles to the face. Another object is to coat the face of such a spinneret with a substance which will repel gas bubbles and neutralize their tendency to adhere to the surface thereof. Other objects will appear hereinafter.

These objects are accomplished by coating the spinneret face with a film of a synthetic thermosetting resin. Preferably, the outside face of the spinneret is coated with a solution of the partially reacted constituents of the resin, and completion of formation of the resin or setting thereof is effected in situ. For example, the outer face of the spinneret may be coated with a solution of a partially polymerized resin which is trans formed subsequently by heat into the hardened infusible form. The resin may be, for instance, a melamine-aldehye, urea-aldehyde, or phenolaldehyde resin; a glycerol-polybasic acid resin; a polyolefine resin, alkyd resin, or the like. Some of the resinous solutions are cationic and can be deposited electrolytically on the spinneret face. For example, a solution of a partially condensed melamine-formaldehyde resin'in dilute hydro-e chloric acid, such as the product available under. the 'tradename Aerotex 607 is cationic and; may be deposited electrolytically. Upon subse-' quent heating the resin is set and, in the final polymerized form is non-ionogenic. Other of the resinous solutions, such as solutions of partially. polymerized ureaand phenol-aldehydes are non-. iogenic and cannot be deposited electrolytically. However, such solutions may be applied by other methods, as by spraying, etc., care being taken to prevent plugging of the spinneret orifices.

The resins forma water-insoluble film on the surface of the spinneret which film is substantially acid and alkali resistant and which does not dissolve in the spinning bath or exert an untoward efiect on the filaments. The resinous solutions may be applied to spinnerets constructed of various metals such as gold, tantalum, plati-' num, and various alloys, the choice of method of application being determined by whether the so lutions are of: the cationic or non-iogenic: type. The resins are effective over a sufficiently prolonged period to permit the obtention of satise.

factory tows which are substantially free of splinters, without requiring, the'spinrr'mgof a.

large number of ends. The orifices maybe distributed in the conventional circular area, butlit will be understood that the invention is notlimited to spinnerets in which. the orifices. are. distributed in an area of any particular shape.

The following examples will illustrate the invention.

Example I A solution of partially reacted melamine-formaldehyde resinsforming components in hydrochloric acidwas deposited electrolytically on the outer surface ofa circular metal'spinneret having a diameter of' twoinches and an orifice area density factor K of 950 when determined by the formula is A where D=orifice density, orifices/sq. in.. S=6.28l3inches A.=3.14= sq. in.

care being exercised to prevent clogging. of the orifices. The spinneret was thensheated'to complete formation of the resin. Viscose was extruded'through the treated spinneret into' an acid spinning bath to form a bundle of individual filaments;

Example II A solution of partially reacted urea-formaldehyde' resineforming; components was sprayed on the outer. face of. aspinneret having a factor'K of 850. The treated. spinneret was then heated to complete formation: of? the resin in situ. Viscose was extruded through the: treated. spinneret to form a bundle of: separate and distinct filam'ents.

While preferred. embodiments of the invention have been shown, it is to be understood that changes and variations may be made without departing: from the spirit andscope of theinvention. as defined by' the appended claims.

We claim;

1. The method: of: producing. filamentary bun.- dies" substantially free of. splinters which com.- prises substantially continuously extrudingv viscose over a prolonged period; of time into'an acid spinningrbath through a metallic spinneret having: an orifice area density factor-Kgreater than SGO'determined by the general-formula K=AD/S where: D is the orifice density of the spinneret expressed as orifices per square inch, S is the periphery of the-spinneretface in inches, and A is. the area of; the spinneret face in: square inches, the outer surface of. the orificed spinneret face being coated with a synthetic thermosetting' resin settothe infusible state.

2. The method of claim 1' in which K has a value upto 950.

The methodof. claim 2 in which the resin is a melamine-aldehyde resin.

4. A. metallic spinneret having an orifice area density factor Kgreater than 800 determined by the formula K=AD/S where D isthe orifice density of the. spinneret expressed as orifices per square inch, S is the periphery of the spinneret face in inches. and Aisthe area of the spinneret face in square inches, the outer surface of the.

4. orificed spinneret face being coated with a synthetic thermosetting resin set to the infusible state.

5. The spinneret of claim 4 in which K has valueup to=.95.0.

61 Thespinneret of claim 5 in which the resin is a melamine-formaldehyde resin.

7; The method of producing filamentary bundlessubstantially free of splinters which comprises substantially continuously extruding viscose over a prolonged period of time into an acid spinning-bath through a metallic spinneret having an orifice area density factor K greater than 800 and up to 950 determined by the general formula K=AD/S where D is the orifice density of the spinneret expressed as orifices per square inch, S is the periphery. of the spinneret face. in inches,. and Ais the area of the spinneretface in square inches, the outer surface of the orificed spinneret face being coated with a. urea-aldehyde resin set to the infusible state.

8'. The method of producing filamentary bun.- dl'es substantially free of splinters which comprises substantially continuously extruding viscoseover a prolonged period of'time into an acid spinning bath through a metallic spinneret having an orifice area density factor K greater than 800 and up to 950' determined by the general formula K'=AD/'S where D is the orifice density of the spinneret expressed as orifices per square inch, Sis the periphery of the spinneret face in inches, and A is the area of'the spinneret face in square inches. the outer surface of the orificed spinneret; face being coated with a phenol-aldehyde resinset to the infusible state.

9'. A metallic spinneret having an orifice density. factor K greater than 800 determined by the formula K=AD/S where D is the orifice density of the spinneret expressed as orifices per square inch, S is the periphery of. the spinneret face in inches, and A is the. area of the spinneret face in square inches, the outer surface of the orificed spinneret face being coated with a urea-formaldehyde resin set'to the infusible state.

10. A metallic spinneret having an orifice area density factor. K greater than 800 determined by the formula K=AD/S' where D is the orifice density of the spinneret expressed as orifices per square inch, S is the periphery of the spinneret face in inches, andA is-the areaof. the spinneret face in square inches, the outer surface of the orificed spinneret face being coated with a phenol-formaldehyde resin set to the infusible state.

DAN; B. WICKER. ELVIN L. COE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name. Date 2,100.581 Weeldenburg' Nov. 30, 1937 2,273,638 Graves Feb. 17, 1942 FOREIGN PATENTS Number Country Date 161,526 Great Britain Mar; 23, 1922 344,327 Germany Nov. 19, 1921 361,735 Germany Oct. 1'7, 1922 364,543- G'ermany Nov. 28, 1931 536,666 Germany Oct. 24, 1931 

